Wireless mesh network technology refers to a network technology that covers a wide area without any connection to a wired network by having access points in an existing wireless LAN equipped with network functions such as multi-hop routing and interconnecting these functions using a wireless communication technology.
In a wireless mesh network, nodes are installed at places not easily reachable by people, or a large number of nodes are installed. Hence, it is difficult to collect the nodes once they are installed, making it difficult to maintain and repair software in the nodes. To solve this problem, a variety of firmware over-the-air (FOTA) technologies for wirelessly updating firmware in nodes have been suggested.
Most of these technologies have their basis in reducing the size of code images for firmware update. By comparing a code image running on a node with a new code image to be transmitted, a differential script, such as the diff program of Linux, which describes the differences between the two code images, is generated. A target node generates a new code image by making the best use of a redundant part between the currently running code image and the code image transmitted to be run by using the thus-generated script.
The method described above has a significant effect of bandwidth reduction because a new code can be generated by transmitting a part of the script if only a part of the existing code image is modified. When changing to a new image totally different from the existing code image, however, the size of the new code image itself may be less than the size of the script.
Meanwhile, in the wireless mesh network, nodes autonomously configure the network, and data is transmitted in a multi-hop fashion. In this environment, to update multiple nodes in a particular area with similar content, it is necessary to transmit similar data multiple times in a multi-hop fashion, which causes bandwidth waste.
For example, FIG. 1 illustrates the concept of sequential network re-programming in a wireless mesh network according to the prior art. As shown in FIG. 1, if a target node needs to be updated, raw images of the same data size are continuously transmitted for update from a base station (BS) 100 to the target node requiring update via intermediate nodes. This results in an increase in the bandwidth usage of the network to update images, leading to unnecessary waste of the bandwidth of the network.